Community biomass accumulation benefits from flexible plant nutrient homeostasis after wildfire

Abstract

As an essential part of the stoichiometric flexibility in regulating the relative tissue contents of nitrogen (N) or phosphorus (P), their homeostasis (H) could determine plant growth under changing nutrient environments, such as under wildfire disturbance. Although a growing number of studies have suggested a coupling relationship between plant nutrient H and species abundance, how leaf N and P homeostasis (HN and HP) regulates the accumulation of community biomass remains unclear, especially in nutrient-fluctuating burned areas. We measured leaf N and P concentrations and total biomass of all species and the soil N and P concentrations across 15 forest plots at four recovery periods (2, 10, 20, and 30 years after burning) with low-severity wildfire and one unburned treatment (>80 years after burning) in boreal forests and associated the community-level HN and HP with biomass accumulation in the Great Xing’an Mountains, China. We found that the HN of trees peaked 20 years after burning under N limitation conditions, and the HP of shrubs approached a maximum at 10 years after burning due to P limitation. It is worth noting that the biomass of trees and herbs was significantly positively correlated with HN, while negative relationships between HP and biomass were shown in trees. Nutrient H explained 59% of the total variation in community biomass, and the joint effect of HN and HP mainly contributed to the biomass accumulation of trees (43.5%) and shrubs (68.5%), respectively. These findings greatly improve the theoretical foundation for understanding how plant nutrient H is associated with biomass accumulation after wildfire. Flexible nutrient H in woody plants highlights the vital role of understory woody species in postfire forest management. Therefore, clearly understanding the relationship between nutrient H and carbon sequestration is essential for a thorough assessment of postfire forest sustainability.